Bis(trimethylsilyl)chromate catalyzed oxidations of alcohols to aldehydes and ketones with periodic acid.
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A facile, selective and high yielding bis(trimethylsilyl) chromate (BTSC) catalyzed selective oxidation of alcohols to aldehydes and ketones with periodic acid is reported. (+info)
Gas-liquid chromatography of bile acids: a new liquid phase for both acetate and trimethylsilyl derivatives.
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Polymetaphenoxylene (PPE-20) has been found to be more useful than cyclohexane dimethanol succinate (HI-EFF-8-BP) for trimethylsilyl derivatives of bile acids and to be preferable to trifluoropropyl substituted silicone (OV-210, QF-1) for analysis of their acetate derivatives. (+info)
Hydrogen and trimethylsilyl transfers during EI mass spectral fragmentation of hydroxycarboxylic and oxocarboxylic acid trimethylsilyl derivatives.
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This paper, describing electron ionization mass spectral fragmentation of some hydroxycarboxylic and oxocarboxylic acid trimethylsilyl derivatives, focuses on the formation of fragment ions resulting from the interactions between the two functionalities of these compounds. These interactions result in the formation of fragment ions at [CH2=C(OTMS)2]+., [CH2=CHC(OTMS)=OTMS]+, [M-31]+, [M-105]+, and [M-RCHO]+. in the case of hydroxycarboxylic acid trimethylsilyl derivatives of formula RCHOTMS(CH2)nCOOTMS and at [RC(OTMS)=CH2]+., [RC(=OTMS)CH=CH2]+, and [M-RC(=O)CH2]+ in the case of oxocarboxylic acid trimethylsilyl esters of formula RC(=O)(CH2)nCOOTMS. Some of these fragmentations appeared to be sufficiently specific to be used to characterize these compounds. Several fragmentation pathways involving trimethylsilyl and hydrogen transfers were proposed to explain the formation of these different fragment ions and were substantiated by deuterium labeling. (+info)
Effects of duration of zilpaterol hydrochloride feeding and days on the finishing diet on feedlot cattle performance and carcass traits.
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A new method for simultaneous determination of cyclic antidepressants and their metabolites in urine using enzymatic hydrolysis and fast GC-MS.
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A method for the simultaneous determination of six commonly prescribed cyclic antidepressants and their major metabolites in urine is presented. This method can be used for quantitation of amitriptyline, nortriptyline, imipramine, desipramine, doxepin, desmethyldoxepin, and maprotiline in human urine, in addition to the qualitative determination of their hydroxylated metabolites. This method is suitable for confirmation of drug abuse in health care professionals and overdose cases where the identity of the abused cyclic antidepressant may not be known. Samples are spiked with internal standard and hydrolyzed with beta-glucuronidase from Escherichia coli. Hydrolysis is found to be essential to the extraction procedure as the tertiary cyclic antidepressants are found to be extensively conjugated in urine. The secondary cyclic antidepressants, on the contrary, are found to be minimally conjugated. Drugs are extracted from alkalinized urine into solvent and derivatized with MSTFA/ammonium iodide/ethanethiol reagent. This reagent produces more stable derivatives compared to reagents previously employed. Gas chromatographic (GC)-mass spectrometric analysis is performed in electron ionization mode by selective ion monitoring, using hydrogen as a carrier gas, a short narrow bore GC capillary column, and fast temperature program, allowing for a rapid analytical cycle. While maintaining specificity for these drugs, concentrations in human urine ranging from 50 to 20,000 ng/mL can be measured with intraday and interday precisions, expressed as variation coefficient, of less than 2.8% for all analytes. (+info)
A convenient synthesis of amino acid methyl esters.
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A series of amino acid methyl ester hydrochlorides were prepared in good to excellent yields by the room temperature reaction of amino acids with methanol in the presence of trimethylchlorosilane. This method is not only compatible with natural amino acids, but also with other aromatic and aliphatic amino acids. (+info)
Lewis acid catalyzed benzylic bromination.
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